Workers WASI

Work in progress

An experimental implementation of the WebAssembly System Interface designed to run on Cloudflare Workers

Usage

import { WASI } from '@cloudflare/workers-wasi';
import mywasm from './mywasm.wasm';

const wasi = new WASI();
const instance = new WebAssembly.Instance(mywasm, {
   wasi_snapshot_preview1: wasi.wasiImport
});

await wasi.start(instance);

Development

Install Rust and nvm then run

nvm use --lts

Build and test

git clone --recursive git@github.com:cloudflare/workers-wasi.git
cd ./workers-wasi
make -j test

Build with Docker

git clone --recursive git@github.com:cloudflare/workers-wasi.git
cd ./workers-wasi
cat ./Dockerfile | docker build -t workers-wasi-build -
docker run --rm -it -v $(pwd):/workers-wasi workers-wasi-build

Testing

We aim to be interchangeable with other WASI implementations. Integration tests are run locally using Miniflare against the following test suites:

Notes

An ephemeral filesystem implementation built on littlefs is included. Both soft and hard links are not yet supported.

The following syscalls are not yet supported and return ENOSYS

fd_readdir
path_link
path_readlink
path_symlink
poll_oneoff
sock_recv
sock_send
sock_shutdown

Timestamps are captured using Date.now() which has unique behavior on the Workers platform for security reasons. This affects the implementation of

clock_res_get
clock_time_get
fd_filestat_set_times
path_filestat_set_times

TODO (remove)

Misc TODO:

path_rename (update old path for existing open fds)
fix preopens interface (use object), and update options docs
document difference between nodejs options and ours (streams/fs)
fd_close (stdio)
fd_renumber (stdio)
fd_read/fd_write does not work with renumbering stdio
update file timestamps appropriately